Epichlorohydrin is a widely used precursor to epoxy resins. Epichlorohydrin is a monomer which is commonly used for the alkylation of para-bisphenol A; the resultant diepoxide, either as a free monomer or oligomeric diepoxide, may be advanced to high molecular weight resins which are used for example in electrical laminates, can coatings, automotive topcoats and clearcoats.
One known method to produce chlorohydrins as reactive intermediates in the manufacture of epoxies, is described in U.S. Pat. No. 2,144,612 in which glycerol (1,2,3-propanetriol, also known as glycerin or glycerine) is converted into an α-chlorohydrin by reaction with anhydrous hydrogen chloride (HCl) in the presence of a catalytic amount of acetic acid (AcOH). U.S. Pat. No. 2,144,612 describes a process that is shown in the following reaction sequence, shown in Scheme 1 below, for making epichlorohydrin via the reaction of glycerol with hydrogen chloride and acetic acid to make glycerol dichlorohydrin. As shown in Scheme 1, epichlorohydrin is produced from the glycerol dichlorohydrin by ring closure in the presence of caustic.

Glycerol is considered to be a low-cost, renewable feedstock and is a co-product of the biodiesel process for making fuel additives. It is known that other renewable feedstocks such as fructose, glucose and sorbitol can be hydrogenolized to produce mixtures of diols and triols, such as glycerol, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol and the like.
With abundant and low cost glycerol or mixed glycols, an economically attractive process for glycerol or mixed glycol hydrochlorination would be desirable. Hydrochlorination of multihydroxylated aliphatic hydrocarbons using HCl is an equilibrium-limited reaction in which water is produced. As the concentration of water builds in the product, the reaction rate declines and the conversion ultimately ceases.
Removal of water by evaporation, azeotropic distillation, reactive distillation or absorption into molecular sieves are known methods used to drive the hydrochlorination reaction further to the desired chlorohydrin product. Despite the considerable capital and processing costs of these water removal techniques, the reaction time for complete hydrochlorination remains greater than about 8 hours due to the inefficiency of these known methods of water removal.
Pending U.S. Patent Publication No. 20080015369 provides a process for producing a chlorohydrin, an ester of a chlorohydrin, or a mixture thereof comprising the step of contacting a crude glycerol an ester of a crude glycerol, or a mixture thereof with a source of a superatmospheric partial pressure of hydrogen chloride, in the presence of a catalyst to produce a chlorohydrin, an ester of a chlorohydrin, or a mixture thereof, said contacting step carried out without substantial removal of water; wherein said crude glycerol, said ester of crude glycerol, or mixture thereof is derived from a renewable raw material. “Superatmospheric pressure” herein means that the hydrogen chloride (HCl) partial pressure is above atmospheric pressure, i.e. 15 psia or greater.
It would be advantageous to further drive the hydrochlorination reaction to the desired chlorohydrin product, thereby decreasing the overall reaction time, by utilization of both superatmospheric conditions and water removal. However, removal of water by evaporation under superatmospheric conditions is not readily accomplished and use of absorption media is difficult to accomplish on an industrial scale.
It would, therefore, be an advance in the art of hydrochlorination chemistry to discover a simple and cost-effective method of transforming multihydroxylated aliphatic hydrocarbons to chlorohydrins (preferably with complete or substantially complete halogenation) under superatmospheric conditions during which water removal is accomplished during the hydrochlorination process by phase separation of the chlorohydrin ester.